The Serbian lost just six times in 2011 after improving his serve, his former Achilles heel, and now Vajda has highlighted the volley as an area to improve.
"This season, I would push him to be more aggressive and go to the net with volleys. The tennis now is not slow, but there are a lot of rallies; the guys are very fit and it's tough to get to the net," Vajda told Sky Sports News.
"But if you can be more aggressive at the beginning of a point, it can be very helpful. Novak is committed to be number one. He was before, he is now and for the future."
Djokovic begins his preparations for the new season against Gael Monfils in the Mubadala World Championships in Abu Dhabi.